Symptoms and control methods of stem blight, Phytophthora blight and southern blight in herb plants
Since herb plants were introduced from abroad by horticultural growers, they have been used not only as seasoning for meals, but also brewed into herbal drinks, or made into herbal bath products. Various forms of use have blended into the daily lives of the general public and are gradually becoming popular. In addition to
Since herb plants were introduced from abroad by horticultural growers, they have been used not only as seasoning for meals, but also brewed into herbal drinks, or made into herbal bath products. Various forms of use have blended into the daily lives of the general public and are gradually becoming popular. Besides large-scale cultivation by horticultural and bed-and-breakfast operators, small potted plants are also very popular among consumers, and herb crops can be seen everywhere on windowsills and in offices. However, because most herb crops were only introduced from abroad in recent years, their disease types and occurrence and damage situations are not well understood. This article only provides a brief introduction to the more common disease types, symptoms and control methods in the field.
1. Stem blight
Pathogen: Rhizoctonia solani Kuhn
Symptoms and occurrence ecology:
A soil-borne fungal disease. In the early stage of symptoms, the part of the stem base in contact with the soil becomes slightly sunken or constricted, and brown lesions then appear, causing the aboveground part to wilt, lodge and die. If leaves come into contact with the affected area, they also show browning and death symptoms. In the later stage, brown irregular small sclerotia may appear on the affected area, which can float with irrigation water and cause secondary infection, or remain in the soil and become the primary infection source for the next season.
Control methods:
1. Diseased plants should be removed immediately together with the root medium to avoid producing sclerotia and increasing the infection source in the field.
2. Apply the antagonistic microorganism Trichoderma sp. developed by the Agricultural Research Institute or National Pingtung University of Science and Technology for biological control.
2. Phytophthora blight
Pathogen: Phytophthora parasitica Dastur
Symptoms and occurrence ecology:
A soil-borne fungal disease. In the early stage, water-soaked lesions appear at the stem base, and under high humidity white thread-like growth can be seen on them. As the disease progresses upward, the aboveground part of the plant shows wilt symptoms, and in severe cases causes plant death. The rainy season or poor drainage easily causes the spread of the disease.
Control methods:
1. Remove diseased plants immediately to reduce pathogen density.
2. Pay attention to drainage in the growing area to avoid excessive moisture.
3. Avoid sprinkler irrigation to prevent disease occurrence and spread.
4. Before the plum rain season arrives, apply phosphorous acid at 1000 times dilution once every 7 days, for 3 to 4 consecutive applications, to induce resistance in plants.
3. Southern blight
Pathogen: Athelia rolfsii (Curzi) Tu et Kimbr. (sexual stage)
Sclerotium rolfsii Sacc. (asexual stage)
Symptoms and occurrence ecology:
In the early stage of infection, plant leaves show yellowing and wilt symptoms. At the stem base, white silky mycelium can be seen lying flat on the surface of the affected area. As the disease progresses, it causes the stem tissue to rot and disintegrate, leading to death of the aboveground part. In the later stage, the mycelium produces round sclerotia 0.5 to 1 mm in size, initially white and later turning light brown, which can float with irrigation water and cause secondary infection, or remain in the soil and become the primary infection source for the next season.
Control methods: same as stem blight